The effect of fission fragment irradiation upon the active to passive transition in the oxidation of self-bonded refel silicon carbide at 850–950°C

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With increasing oxidant pressures there can be two successive modes of oxidation (active and passive) of silicon carbide and silicon, resulting in the formation of either volatile silicon monoxide, or a protective silica layer. The active corrosion of REFEL silicon carbide, containing ≈ 16% free silicon, has been examined experimentally out-of-reactor at lower temperatures than previously and has been shown to occur at 900 and 950°, but not at ⩽ 875°C. The oxygen pressures for the transition to the passive type of oxidation were not greater than those calculated on the basis of a theoretical model. Irradiation with a fission fragment flux of 1 × 10 11 ff/cm 2 · sec did not affect significantly either the minimum temperature for the onset of active corrosion or the active-passive oxidation transition pressure, at temperatures up to ≈ 950°C.